When a cell membrane is said to be selectively permeable, it means that the cell membrane controls what substances pass in and out through the membrane. This characteristic of cell membranes plays a great role in passive transport. Passive transport is the movement of substances across the cell membrane without any input of energy by the cell. The energy for passive transport comes entirely from kinetic energy that the molecules have. The simplest type of passive transport is diffusion, which is the movement of molecules from an area of high concentration to an area of lower concentration. Diffusion moves down the concentration gradient, which is the difference in the concentration of molecules across a space. Osmosis is a type of diffusion in which water molecules move down the concentration gradient.

When the concentration of solute molecules outside the cell is lower than the concentration of solute in the cytosol , the solution outside is hypotonic to the cytosol. If the concentration of solute molecules is higher outside of the cell, the solution outside is said to be hypertonic. The solution outside is isotonic if the concentration is equal on both sides of the cell membrane.

The egg shell is made of calcium carbonate and vinegar contains acetic acid. These two can react to produce calcium acetate and carbonic acid which then decompose into water and carbon dioxide as shown in the two chemical equations:

The eggs will increase in mass in all three solutions, showing that diffusion and osmosis occur when the concentration of two solutions is different, so that equilibrium can be established.

Materials:

To conduct this experiment, these materials will be needed: 1-2 fresh hen eggs in their shells, masking tape and marker, distilled water, clear sugar syrup, vinegar, clear jar with lid, tongs, electronic balance, paper towels, paper, and a pencil.